1. Field of the Invention
The present invention relates to a lubricant deterioration detecting device for detecting the status of deterioration of a lubricant resulting from admixture of an alien substance and also to a detecting device incorporated bearing assembly equipped with such lubricant detection detecting device such as, for example, a detector incorporated bearing assembly for use in railway vehicles, automotive vehicles and industrial machines or the like.
2. Description of the Prior Art
In the bearing assembly filled with a lubricant, an insufficient lubrication occurs once the lubricant (such as, for example, a grease or oil) within the bearing assembly is deteriorated, resulting in a reduction in lifetime of the bearing assembly. Since determination of the occurrence of the insufficient lubrication in reference to the status of vibration or the like occurring in the bearing assembly is carried out when and after an operating abnormality has occurred as a result of expiration of the lifetime of the bearing assembly, the presence or absence of an abnormality in lubrication cannot be carried out at an early time. In view of this, it has been desired to monitor the status of the lubricant within the bearing assembly regularly or in real time so that the occurrence of the abnormality and/or the time for maintenance can be predicated.
A major cause of deterioration of the lubricant may include an admixture of powdery wear debris, which is produced as the bearing assembly is used, into the lubricant.
For detecting the status of wear of the bearing assembly, a sensor incorporated bearing assembly has been suggested, in which a sensor in the form of an electrode or a coil is arranged inside a sealing member of the bearing assembly so that the electrical characteristic of the lubricant resulting from the admixture of the wear debris can be detected. (See, for example, the Japanese Laid-open Patent Publication No. 2004-293776, published Oct. 21, 2004.)
However, since the sensor incorporated bearing assembly disclosed in the above mentioned patent document is so designed that the electrical characteristic of the lubricant can be detected, no change in characteristic can be detected unless a condition is established in which conduction occurs as a result of inclusion of a substantial amount of wear debris, and thus, difficulty often occurs in detecting the inclusion of the alien substance.
In order to alleviate the problems discussed above, such an optical construction, although it has not yet been known, has been contemplated, in which, for example, as shown in FIG. 25, an light emitting element 53 and a light receiving element 54 are arranged, with a lubricant 55 intervening therebetween, so that the status of deterioration of the lubricant 55 can be estimated from the intensity of light emitted from the light emitting element 53 and subsequently detected by the light receiving element 54.
In the case of the above described construction, it has been found that where the thickness d of the lubricant 55 forming an object to be detected changes as shown by the broken line in FIG. 25, the intensity of light detected by the light receiving element 54 changes correspondingly, and any provision is therefore needed to maintain the thickness d of the lubricant 55 at a constant value.
In view of the above, such an alternative construction, although it has also not yet been known, has been contemplated, in which, for example, as shown in FIG. 26, one end of an optical fiber 56 on a light emitting side and one end of an optical fiber 57 on a light receiving side are so arranged as to oppose to each other with the lubricant 55 intervening therebetween and the light emitting element 53 and the light receiving element 54 are arranged in proximity to the other ends of the optical fibers 56 and 57 on the light emitting and receiving sides, respectively.
With the construction shown in FIG. 26, rays of light emitted from the light emitting element 53 are transmitted across the lubricant 55, positioned at a measuring site 58, through the light emitting optical fiber 56 and are subsequently detected by the light receiving element 54 through the light receiving optical fiber 57, whereby the amount of foreign matter admixed in the lubricant 55 can be estimated from the intensity of the transmitted light detected by the light receiving element 54. In this case, since the surface area of each of the optical fibers 56 and 57 at the measuring site 58 can be minimized, ingress of the lubricant 55 into the measuring site 58 can be facilitated and the lubricant once entering the measuring site 58 can easily be maintained at a constant thickness.
However, even with the construction shown in FIG. 26, the measuring site 58 requires a vessel of a structure designed to maintain the thickness d of the lubricant 55 at a constant value and, therefore, the freedom of arrangement within, for example, a bearing assembly is lowered particularly where it is used in detecting the status of deterioration of the lubricant of a kind sealed within the bearing assembly.